KR20190057409A - Boron nitride agglomerates, method for producing same, and use thereof - Google Patents

Abstract

The present invention relates to a boron nitride aggregate comprising layered hexagonal boron nitride primary particles and having a first orientation property and agglomerating with each other and formed into a flake shape.
The present invention also relates to a process for producing the above boron nitride aggregates wherein the layered hexagonal boron nitride primary particles are agglomerated in such a way that they have a preferential orientation and are aligned with each other.
The flaky aggregate according to the present invention is suitable as a filler for a polymer to form a polymer-boron nitride composite and as a filler for hot compression of a boron nitride sintered body.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a boron nitride agglomerate, a method for producing the same,

The present invention relates to a boron nitride aggregate comprising layered hexagonal boron nitride, a process for preparing the same, and a method of using the boron nitride sintered body for hot pressing as a filler for a polymer.

Due to its excellent thermal conductivity, the hexagonal boron nitride powder can be used as a filler for polymers in applications requiring simultaneous excellent insulating ability of the filler used. In addition, the boron nitride powder is used for hot pressing or as a sintered powder for metallurgical fields. Moreover, the hexagonal boron nitride powder is used as a lubricant in the production of cosmetics, as one of the compounds in metallurgy, and as a raw material for producing equiaxed boron nitride.

The hexagonal boron nitride powder is industrially synthesized through a nitridation reaction of boric acid in the presence of a nitrogen source. Ammonia is used as a nitrogen source, and calcium phosphate is used as a carrier material for boric acid. Organic nitrogen sources such as melamine or urea may react with boric acid or borates under a nitrogen atmosphere. The nitridation reaction is usually carried out at a temperature of 800 to 1200 ° C. Thereafter, the obtained boron nitride is mostly amorphous and is called turbostratic boron nitride. The hexagonal crystal growth type boron nitride is preferably produced from amorphous boron nitride at a high temperature of up to about 2100 DEG C under a nitrogen atmosphere. For this high-temperature treatment, a crystalline additive may be added to the amorphous boron nitride.

In the high temperature treatment, hexagonal boron nitride (hBN) is formed as primary particles in the form of a layer. The size of the thin film layer is usually in the range of 1 to 20 mu m, but the size of the thin film layer can be 50 mu m or more at the most. Generally, the heat-treated product is produced and then ground or pulverized to obtain a workable powder.

The thermal conductivity of the hexagonal boron nitride is larger in the direction in which the layer plane (a-axis) direction is perpendicular to the direction (c-axis). The thermal conductivity in the c-axis direction is 2.0 W / mK, while the a-axis direction is 400 W / mK (RF Hill, SMTA National Symposium "Emerging packaging Technologies", Research Triangle Park, NC, Nov. 18-21, 1996 Reference).

The hexagonal boron nitride powder to be used as a filler, similarly to the primary particles of the layered boron nitride formed in the synthesis of hexagonal boron nitride, or the aggregates thereof, can also be produced in the form of a granule specifically prepared, i.e., a secondary particle formed from primary particles It is often used. Granulation improves the processability, such as free flowing properties and measurement properties of the nitrified grain powder, and can achieve high filling degree and high thermal conductivity, for example, in a polymer-boron nitride composite. There are various methods for producing these secondary particles, thereby providing granules having various shapes and various properties.

Specially prepared granules are referred to as " aggregates ", which refers to agglomerates or agglomerates formed during the synthesis of hexagonal boron nitride.

Conventional technology

Known methods for producing granules include pelleting and spray granulation. The starting point of spray granulation is when a solid suspension is produced in the liquid phase, which is sprayed with droplets and then dried. In the case of pelleting, the addition of a small amount of liquid to the solid leads to the aggregation of the solid primary particles by surface wetting and capillary forces, and the resulting aggregates are dried. In both of the above methods, a binder is usually used. Secondary particles of low density and high porosity are obtained by both of the above methods.

U.S. Patent Application US 2006/0127422 A1 discloses a method of making spherical boron nitride agglomerates wherein the hexagonal boron nitride is spray dried from an aqueous suspension containing an organic binder. Spherical boron nitride granules having a size of 1 to 500 mu m are obtained by spray drying. In contrast to the initial powder, the sprayed granules are fluid.

International patent application WO 03/013 845 A1 discloses a process for the preparation of spherical boron nitride granules wherein the hexagonal boron nitride primary particles are spray dried with a polycarboxylic acid, silane or organometallic compound, The spray-treated granules are sintered at a temperature of 1800 to 2400 ° C.

The boron nitride granulation method by spray drying has a disadvantage that a binder must be used and the organic binder used for spray drying must be adjusted to a specific system for further processing as a polymer filler. Since the granules obtained by spray drying are low-density, when they are used as fillers for thermoplastics, the aggregates can be completely collapsed.

One possible method for making high density boron nitride granules is milling of hot pressed boron nitride. As a result of this treatment, high-density granules corresponding to the density of the hot-pressed compaction bodies are obtained. However, this method suffers from the disadvantage of producing hot-compacted boron nitride from boron nitride powders (i.e., boron nitride primary particles) at a temperature of about 1800 ° C and an axial consolidation pressure of typically 20 MPa, This is the process. The subsequent processing steps of the special milling of the hot press are also expensive.

Other methods of making boron nitride granules for use as fillers are disclosed in U.S. Pat. No. 6,048,511 and European Patent EP 0 939 066 A1. In these patents, the hexagonal boron nitride powder is processed into particles, the size distribution of which is in the minimum size range of 100 mu m, and the polished hBN powder is cold-compacted. Thereafter, the granules are prepared from the cold compact by means of a disintegration process, and finally sieving the resulting granules to obtain agglomerates having a desired range of sizes. The disintegration and cold pressing steps can be repeated several times to consolidate to a density of up to 1.91 g / cm 3, by which granules are produced by decay. This method has the disadvantage that it requires an initial powder of a certain size distribution and therefore requires a plurality of steps for consolidation and comminution, which is very costly.

In US patent application US 2002/0 006 373 A1, briquettes of a boron nitride coagulated thin film layer formed during the production of hexagonal boron nitride in a high-temperature treatment process at 1400 to 2300 ° C under a nitrogen atmosphere were polished to obtain hexagonal boron nitride aggregate And an unfused boron nitride plate, and the unfused platelets are removed to obtain a powder composed of an aggregate of a hexagonal boron nitride plate having a size distribution of 10 to 125 mu m.

US application US 2004/0208 812 A1 describes a method for producing boron nitride powders containing boron nitride agglomerates wherein hexagonal boron nitride having an average plate size of at least 2 microns is compacted with a green compact And then the green compact is sintered at a temperature of about 1400 ° C at a density of 1.4 to 1.7 g / cm 3 at maximum, and then the sintered compact is polished.

International patent application WO 2005/021428 A1 describes a process for preparing low density and medium density boron nitride agglomerates wherein turbo static or hexagonal boron nitride powder having a maximum particle size of 5 μm is heated to a temperature of 1400 ° C or higher, Heat treatment is performed at 1850 to 1900 占 폚, and then the wafer is polished. Before the heat treatment, the boron nitride powder may be compressed into a compact by isostatic pressing and polished.

The resultant aggregates are spherical or cubic, and the aggregates are isotropic. That is, the primary particles are unoriented in the aggregate.

U.S. Pat. No. 5,854,155 and US Pat. No. 6,096,671 describe a method for producing agglomerated layered boron nitride particles, wherein the boron nitride thin film layer is non-oriented in agglomerates. That is, they do not have a preferred direction and are bonded together without a binder. The boron nitride aggregate is in the form of a pine cone and is already formed during the synthesis of hexagonal boron nitride using boric acid, melamine and a crystallization catalyst. These agglomerates are very dense and have low mechanical stability.

A common feature of the above-described processes in the production of boron nitride granules is that these granules are all composed of non-oriented layered boron nitride grains. When used as a filler to increase the thermal conductivity of a polymer, the layered form of hexagonal boron nitride is disadvantageous (as described on page 2 of WO 03/013845 A1). Due to the small primary particle size and often associated high specific surface area of the hexagonal boron nitride powder, processing and applicability are limited. The processability can be improved by producing an isotropic aggregate having a non-oriented hBN thin film layer.

When boron nitride powders are used as fillers for polymers, the goal is to achieve the highest possible thermal conductivity for the polymer-boron nitride composite, thereby maximizing the elimination of any heat generated. To achieve a certain value of thermal conductivity in a polymer-boron nitride composite, the degree of filling and the amount of boron nitride used should be as small as possible.

In the case where the boron nitride primary particles contained in the polymer-boron nitride composite are oriented isotropically, that is, when they do not have preferential orientation, the excellent thermal conductivity of boron nitride in the layer plane (" in- You may not be able to make full use of it. That is, the material frequently occurs not only in thermal conductivity in the layered plane of hexagonal boron nitride but also in a direction perpendicular to the layer plane of hexagonal boron nitride. When an isotropic boron nitride aggregate in which the primary particles in the aggregate do not have an orientation is used in the production of the composite, the distribution of the boron nitride primary particles in the polymer-boron nitride composite is also isotropic and the excellent thermal conductivity of the boron nitride in the layer plane I can not use it properly.

As with the manufacture of granules, various methods for increasing the thermal conductivity of boron nitride filled polymers have been described.

For example, US patent application US 2003/0 153 665 A1 describes a method of applying a magnetic field to a polymer mixture containing hexagonal boron nitride powder. In this method, a boron nitride thin film layer containing hexagonal boron nitride powder is oriented in a specific direction, and then the polymer mixture containing the oriented boron nitride powder is cured. With this method, a filled polymer having increased thermal conductivity in the orientation direction of the boron nitride thin film layer can be obtained. However, this method has a disadvantage of requiring an external magnetic field to orient the boron nitride thin film layer.

International patent application WO 2008/085 999 A1 describes the preparation of a polymeric material filled with boron nitride, wherein the hexagonal boron nitride is mixed with the polymer and then cured by pressing, e.g., by extrusion, . For example, several samples of 1 mm in thickness prepared in the above manner are laminated in order and hot-pressed at 130 캜. The disk obtained from this compact is machined perpendicular to the orientation direction of the boron nitride thin film layer. The through-plane thermal conductivity measured from the resulting disk is higher than the thermal conductivity of the originally manufactured liner. However, this method is expensive, and can not be used for all purposes, since the sample must be removed perpendicular to the orientation direction of the boron nitride thin film layer. For example, the method is only suitable for thermoplastics, and is not suitable for thermosetting resins or pastes.

Therefore, it is an object of the present invention made to overcome the drawbacks of the prior art that it is possible to use high-density boron nitride aggregates, and to have an anisotropy of hexagonal boron nitride and, in particular, Boron < / RTI > aggregates.

Another object of the present invention is to provide a cost effective and simple method for producing high density boron nitride aggregates and a method of using the same.

In order to achieve the above object, the present invention provides a method for producing a boron nitride aggregate according to claim 1, a method for producing a boron nitride aggregate according to claim 11, a polymer-boron nitride composite according to claim 17, Thereby obtaining the sintered boron nitride.

Accordingly, the present invention relates to a boron nitride aggregate comprising layered hexagonal boron nitride primary particles, wherein the aggregate has a flake-shaped shape, the aggregate having a preferential orientation.

The present invention also relates to a method for producing boron nitride aggregates, wherein the layered hexagonal boron nitride primary particles are agglomerated in such a manner that they are arranged side by side with preferential orientation.

The present invention also relates to a polymer-boron nitride composite comprising a flake-shaped boron nitride aggregate according to the invention and a boron nitride sintered body obtainable by sintering the flake-shaped boron nitride aggregate according to the invention.

In contrast to known aggregates in which the boron nitride in the aggregate is preferentially non-oriented, the primary particles in the aggregate according to the invention have a defined preferential orientation. That is, these particles are oriented and agglomerated with respect to each other. The boron nitride agglomerates according to the present invention are based on preferential orientation of boron nitride primary particles and can also be defined as textured boron nitride aggregates.

The boron nitride aggregate according to the present invention is in the form of flakes and may be referred to as " flakes " based on the flake shape. Such flakes according to the invention are also micronized in non-flocculated layered boron nitride primary particles, often referred to as " flaky boron nitride particles ". The structure of the aggregate according to the present invention consists of a plurality of individual boron nitride thin film layers.

In contrast to non-aggregated boron nitride powders, the aggregates according to the invention are free-flowing and can be easily quantified.

The organized aggregates according to the invention are dense and may be higher than the dense aggregates disclosed in EP 0 939 066 A1.

Further, the agglomerates according to the present invention have good mechanical stability, and this mechanical stability can be remarkably improved by heat treatment of agglomerates.

Due to preferential orientation of the boron nitride primary particles in the aggregate, in contrast to the known aggregates, the aggregates according to the present invention are anisotropic. Particularly, the thermal conductivity of the flake in the radial direction is higher than the thickness direction of the flake. This is because heat conduction occurs largely in the plane of the thin film layer of boron nitride primary particles having high thermal conductivity in the direction of the diameter of the flake, that is, the plane of the flaky aggregate.

Surprisingly, it has been found that aggregates with high density and good mechanical stability can be prepared by the process according to the invention.

It is also an unexpected finding that, in contrast to known isotropic granules with little or no texturing, it is possible to produce highly structured boron nitride aggregates having a very strong orientation to each other of boron nitride primary particles . The texture is also significantly greater than hot-pressed boron nitride.

Compared to known processes in the prior art for boron nitride granules, the process of the present invention is advantageous for low cost, high density granules in a single process, and also for continuous processes for producing large quantities of boron nitride aggregates.

Surprisingly, the structured boron nitride agglomerates according to the present invention can also be used as fillers for polymers, and thus a high thermal conductivity value can be obtained. The above facts are surprising since the thermal conductivity anisotropy of the primary particles and the layered particle morphology of the primary particles have been considered to be undesirable for application as a filler. These disadvantages were also overcome by manufacturing and using isotropic granules.

Because of the anisotropy of the agglomerates according to the present invention, the anisotropic heat conduction properties of hexagonal boron nitride can be better exploited. Polymers filled with isotropic boron nitride agglomerates, spherical and cubic, also have isotropic heat conduction properties. The anisotropy of the thermal conductivity of the polymer-BN composite can be controlled by using the anisotropically ordered boron nitride aggregates according to the present invention. In the case of using a layered structured agglomerate, for example, in the injection molding of a corresponding polymer-boron nitride compound, that is, in the case of plates or ribs, due to wall friction, the polymer- Boron complex is obtained. The polymer-boron nitride composite produced in this manner has orientation of agglomerates in a preferential direction and has a thermal conductivity value in a preferred direction (" in plane " with respect to the plane of the thin film layer) perpendicular to the preferential direction "). It is a surprising discovery that when using such a polymer-boron nitride composite, a high thermal conductivity value can be obtained not only in a plane but also in a plane pass.

In contrast to some methods disclosed in the prior art for the preparation of boron fluoride granules or agglomerates, it is possible to produce binder-free agglomerates by the process according to the invention.

Figure 1a shows an SEM micrograph of an aggregate according to the invention having a smooth formed surface and a rough, cracked surface.
1B shows a schematic view of a SEM micrograph of FIG. 1 showing a smooth forming surface 1 and a rough and cracked surface 2. FIG.
Fig. 2 schematically shows a process for producing an aggregate according to the invention, which is consolidated when two rolls (3, 4) arranged without a gap are driven when one of them is driven.
Fig. 3 schematically shows a powder filler 5 on the rolls 3, 4, in which the particles to be agglomerated are oriented in a narrow region above the " roll gap ".
Figure 4 schematically shows the filled roll interval 6 in which the pre-oriented particles are fully oriented and consolidated under high pressure in the roll interval to form a high density of organized agglomerates. If the thickness of the agglomerate is about 50 microns, the organized agglomerates force the two rolls apart at an interval of 50 microns.
Figure 5 shows a schematic cross-section of a structured aggregate (7) structure according to the invention in which the hexagonal boron nitride primary particles 8 are densely packed and predominantly oriented parallel to one another. That is, they have preferential orientation with respect to each other. The roughness of the forming surface (upper and lower surfaces of the schematics) is within the thickness range (<1 μm) of the primary particles. The surface roughness of the side region, that is, the crack plane or edge region formed during consolidation, is within the average diameter range of the primary particles.
Figure 6 schematically illustrates a suitable milling method for producing structured agglomerates, for example, a method of cutting or breaking structured boron nitride agglomerates perpendicular to the forming surface, and the resulting oriented agglomerates of boron nitride primary particles Is a reverse or rotational direction. The orientation of the primary particles in the newly formed aggregates is not parallel and is perpendicular to the main surface of the aggregate. Organized agglomerates prepared in this manner can be oriented in the polymer-boron nitride complex during the formation process, and as a result, planar thermal conductivity can be increased.

As described above, the boron nitride agglomerates according to the present invention are agglomerates of layered hexagonal boron nitride primary particles, which are initially oriented and aggregated with each other, and are therefore also referred to as oriented or organized agglomerates or granules.

Preferably, the boron nitride primary particles are preferentially oriented and aggregated in such a manner that the thin film layer planes of the boron nitride primary particles are arranged essentially parallel to each other. In other words, most of the boron nitride initial particles are oriented parallel to each other or nearly parallel.

The degree of orientation of the layered boron nitride primary particles in the aggregate according to the present invention may be characterized by a texture index. In the case of hexagonal boron nitride having the isotropic orientation properties of the layered boron nitride primary particles and therefore having no orientation, the structure index is one. The tissue index increases with the orientation of the sample. The tissue index of the aggregate according to the present invention is more than 1.5, preferably not less than 2.0, more preferably not less than 2.8, particularly preferably not less than 3.5. The tissue index of the aggregates according to the invention may also be a value of at least 5.0 and at least 10.0.

The tissue index is measured by X-ray method. In this case, the intensity ratio of the (002) and (100) reflection measured in the X-ray diffraction diagram is determined and divided by the corresponding intensity ratio of the ideal untextured hBN sample. The ideal ratio can be determined from the JCPDS data, which is 7.29.

Therefore, the tissue index (TI) can be determined by the following equation.

A high tissue index value of 100 or more can be obtained in the aggregate according to the present invention having a size of about 3.5 cm 2 (with respect to the area of the upper and lower surface of the flaky aggregate). These values, measured in large flake agglomerates, provide evidence of the pronounced orientation of the primary particles in the aggregates according to the invention. Tissue indices of smaller aggregates, e. G. Agglomerates having a size of less than 1 mm, are measured in the layer of agglomerates. Next, there is a partial random orientation in the sample carrier for X-ray measurements. Thus, the values obtained in less organized aggregates relative to the tissue index are always less than those corresponding to the orientation of the primary particles in the individual flake agglomerates.

The aggregate size in the aggregates according to the invention can be said to be, for example, the mean aggregate size (d ₅₀ ) determined by measuring the sieving fraction of "<350 μm" or "100-200 μm" have. The aggregate size distribution can be measured by laser diffraction (dry measurement, Mastersizer 2000, Malvern, Germany).

Aggregates according to the present invention may have agglomerate sizes of a few centimeters. In subsequent processing or use, agglomerate sizes of up to 1 cm or more are appropriate, depending on the particular application. When used as a polymeric filler, a very wide variety of materials are typically used as agglomerate sizes of up to 3 mm, preferably up to 1 mm. Preferably an average aggregate size (d ₅₀ ) of at most 500 μm, more preferably at most 200 μm. The d ₅₀ value is preferably at least 30 탆. Particularly, the particle size range to be used is preferably narrow, and for example, a range of 100 to 300 mu m, 1 to 2 mm, or 50 to 150 mu m is used.

The flaky aggregate according to the present invention may have a thickness of 10 to 500 mu m, preferably 15 to 350 mu m, particularly preferably 30 to 200 mu m.

The aspect ratio of the flaky aggregate, that is, the contrast of the aggregate diameter to the aggregate thickness, can be determined based on the SEM photograph by measuring the aggregate diameter and thickness.

The aspect ratio of the flaky aggregate according to the present invention has a value greater than 1, preferably a value of 1.5 or greater, more preferably 2 or greater.

The density of the aggregate according to the invention is preferably 1.6 g / cm3, more preferably 1.8 g / cm3, or even more preferably 2.0 g / cm3 or more.

The density of the aggregates according to the present invention can be determined for agglomerates having a size of about 1 to 5 cm 2 according to the principle of Archimedes as buoyant density in water or for agglomerates obtained by cutting to a size of about 1 cm x 1 cm It can be measured geometrically.

When used as a polymeric filler, it is advantageous to use a filler or aggregate with the smallest possible surface area (BET). This is because heat transfer resistance from the filler to the polymer can be minimized in this case. By using the method according to the present invention, it is possible to produce aggregates of boron nitride having much smaller surface area than aggregates according to the prior art.

The structured agglomerates according to the present invention have surfaces directly formed on the upper and lower sides in accordance with the formation process, not by pulverization. These surfaces are defined as " forming surfaces ", and are relatively smooth as opposed to the rough sides (cracked surfaces) of agglomerates produced by crushing or grinding operations. The surface of the flaky aggregate according to the present invention is essentially flat and its top and bottom are substantially parallel to each other.

The ratio of the forming surface to the entire surface of the aggregate according to the present invention is at least 33% (if the diameter of the aggregate is equal to height), assuming a layered or flaky shape with a circular major surface, Assuming a layered or flaky shape with a major surface, it is at least 33% on average (in the case of a cube). In the aggregate according to the invention having a large aspect ratio, the ratio of the forming surface to the overall surface is much larger; For example, in the case of an aggregate having an aspect ratio of more than 3.0, the formed surface ratio is about 60 to 95%, and in the case of a large aggregate, the above ratio can be larger. Although the aggregate surface is subjected to rounding treatment, sieving or sorting processes, etc., the ratio of forming surface to the entire surface is reduced, but this ratio is essentially at least 10%, preferably at least 20%.

The ratio of the formed surface to the entire surface can be determined by SEM photo analysis. For determining the aspect ratio, the values determined from the aggregate diameter and thickness are used for the above purposes. The ratio of the formed surface in the entire plane is determined from the above values as follows:

Surface area ratio [%] = 2 * Front area / Total area * 100

here,

Front area = aggregate diameter * Agglomerate diameter

Total area = 2 * Front area + 4 * Side area

Side area = aggregate thickness * Agglomerate diameter

In the preparation of the structured agglomerates according to the invention, preferably the boron nitride powders of hBN are consolidated between the two counter-rotating rolls to form organized agglomerates.

At this time, the starting material containing the boron nitride powder or the boron nitride powder to be used for coagulation is continuously fed into the space between the two counter-rotating rolls in a uniform amount. Since the rolls rotate in opposite directions, the shear action of the aggregate is minimized. The distance, i.e., the inter-roll distance, is preferably at most 500 μm. In a preferred embodiment, the rolls are pressed together at a certain contact pressure. As a result, these rolls come into contact with each other without a gap being opened. The boron nitride powder thus supported or adhered is strongly pressed between the rolls. If there is no gap between the two rolls, the roll is forced apart by the organized agglomerates during consolidation, and the resulting gap corresponds to the thickness of the agglomerate. The material used for roll making should have the maximum possible hardness so that the shape of the roll gap can be maintained without deformation. The roll can be made of a ceramic material such as silicon nitride.

In the process of quantifying the amount of boron nitride powder entering the space between the two rolls, a sufficient amount of boron nitride powder can be introduced into the space between the two rolls, . If the supply amount is insufficient, the compressibility is insufficient or the compression is not performed, and it is difficult to form agglomerates. If the metering is sufficient, the filling amount can be maximized beyond the gap between the rolls depending on the roll shape, rolling parameters and initial powder. If the weighing is exceeded, the area exceeding the gap between rolls is called "overflow". If the starting material used is too rough, the roll may be locked and the roll gap may also be clogged.

It is also possible to provide a roll having a surface structure. For example, a surface structure may be used to obtain the fracture point of the flaky aggregate needed to determine the size and shape of the aggregate. The consolidated agglomerates can therefore be easily comminuted to form agglomerates of a certain size and shape. Also, through the structure of the roll, for example, the shape of a planar-polygonal aggregate can be made.

The boron nitride powder may be hexagonal boron nitride and may be a mixture of hexagonal boron nitride and partial boron nitride having irregular boron nitride.

The average particle size (d ₅₀ ) of the hexagonal boron nitride powder used herein may be 0.5 to 50 μm, preferably 0.5 to 15 μm. For example, hexagonal boron nitride powders having an average particle size of 1, 3, 6, 9 and 15 microns can be used, but larger mean particle sizes of up to 50 microns are also possible. Mixtures of various hexagonal boron nitride powders having different particle sizes may also be used. The average particle size (d ₅₀ ) of the boron nitride powder is generally measured by laser diffraction (wet measurement, Mastersizer 2000, Malvern).

B ₂ O ₃ -free boron nitride powder and a low B ₂ O ₃ content of at least 0.5% by weight boron nitride powder, as well as at most 10% by weight or more of high B ₂ O ₃ content boron nitride powder can be used.

Further, for example, agglomerates formed in the course of synthesis of boron nitride granules such as pelletized granules and spray granules of hexagonal boron nitride and hexagonal boron nitride can also be used. Boron nitride used for rolling consolidation can be surface-coated with an additive. The additive is preferably a polymer, an organometallic compound, a silane, an oil, a carboxylic acid, a copolymer, a hydrolyzed monomer, a partially hydrolyzed monomer, Condensation monomers and nanoparticles.

Mixed aggregates (" hybrid flakes &quot;) may also be prepared using a mixture of pulverulent or granular boron nitride and other powders. These other powders may be selected from the group consisting of carbides, borides, nitrides, oxides, hydroxides, carbon and metals. Such materials can be used as particles, in the form of fibers or thin films of any desired degree of granularity. In addition, the polymer can be processed with boron nitride to form organized aggregates. For example, SiO ₂ powder, preferably nano-sized SiO ₂ powder such as fine powder silica, or aluminum oxide, boehmite or Al (OH) ₃ , preferably nano-sized powder, or aluminum nitride, May be added to the powder. When metal particles are added, they can be heat treated in a nitrogen atmosphere to form a nitride, which is then consolidated. In addition, polymers and precursors of ceramic materials, such as salts and alkoxides, may be added. Mixtures of such additives can also be used with hexagonal boron nitride for the preparation of mixed granules and the mixed granules from these powder mixtures can also be used for consolidation. Granular additives may also be used, which may be used in admixture with powders or granular boron nitride, the starting material of consolidation.

Upon compaction, the spraying of the hexagonal boron nitride powders and the pelletized granules can be used with sol-gel binders such as beehmite, MTEOS (methyltriethoxysilane), sodium silicate, silica sol and mixtures thereof with nanoparticles A sol-gel system such as a sol-gel-coated boron fluoride powder and a mixture of behemite, MTEOS (methyltriethoxysilane), sodium silicate, silica sol and the nanoparticles may be used for coating.

Depending on the nature of the powder material, and especially their initial particle size and particle distribution, flakes are formed with different sizes and different diameters and uniform thicknesses during roll-through, usually in the presence of unconsolidated material fragments.

Consolidation can be repeated several times. Upon consolidation two or three times, the uncompacted fines fraction may be reduced to a maximum of 50 wt.% To 5 wt.% Or less. An increase in the size of the agglomerate is also observed with respect to diameter and thickness.

Between consolidation of two consecutive steps, the resultant uncompensated fine particles can be sieved and returned to the previous stage.

However, the particulate matter may be left alone with the consolidated product without being separated. In this case, the resulting particulate is minimized in a subsequent compression step as it is also consolidated into agglomerates.

When a fine starting material having an average particle size (d ₅₀ ) of about 1 탆 is used, agglomerates having a granule size of 1 to 4 mm can be obtained by primary consolidation. Upon secondary consolidation, the diameter of the aggregate may increase to about 1 cm. In the final consolidation, a structured agglomerate of up to 2 cm in size can be obtained.

When using a coarse starting material of primary particles having an average particle size (d ₅₀ ) of 15 μm, for example, a structured agglomerate of 1 to 2 cm in size can be obtained in the first pass, 4 cm in size, and agglomerates of 5 to 7 cm in the final consolidation step.

When the starting material used is pelleted granules, spray granules or similar granules rather than powders, a first pass of a few centimeter sized organized agglomerates from particles having an average granular size of about 100 to 200 [mu] m, and an "unlimited" agglomerate And is obtained at the time of the second passage.

Consolidation is carried out selectively according to the starting material to be used, and it is advantageous to carry out a protective sieving or sorting step together to prevent damage or interruption of the roll.

Agglomerated materials can be subjected to a heat treatment step and a sintering step. Heat treatment of the agglomerates improves mechanical stability and thus improves processability, e.g., metrology.

The thermal conductivity attainable in the boron nitride polymer composite can also be further increased by the sintering process of the flaky aggregate.

Heat treatment can change the properties of agglomerates and primary particles. The degree of crystallization of primary particles increases, which is related to the growth of primary particles. The lattice oxygen content and surface area decrease as the heat treatment temperature increases and the heat treatment period is prolonged. Density, hardness and mechanical stability can be maximized depending on the heat treatment temperature and the heat treatment period.

Depending on the sintering conditions and the nature of the organized agglomerates, loose individual agglomerates with a crunching sound of the ceramic are obtained or milled by shaking, screening or the like to be separated into compact aggregates A sintered cake composed of agglomerates is obtained.

The heat treatment can be carried out under a protective gas atmosphere at a temperature of up to 2300 占 폚, preferably between 1200 and 2050 占 폚, more preferably between 1400 and 2000 占 폚, and particularly preferably between 1600 and 1950 占 폚. In the case of mixed agglomerates (hybrid flakes), the heat treatment can be carried out in a protective gas atmosphere at a maximum temperature of 2000 ° C or in air, and may be carried out, for example, with a reactive gas such as ammonia gas or carbon monoxide or a gas mixture. After reaching the maximum temperature, up to several hours or several days of maintenance can be applied. Nitrogen or argon can be used as a protective gas. The heat treatment can be performed by a continuous process or a batch process.

After consolidation, or alternatively after a subsequent heat treatment, the resulting aggregates or sintered cakes can be processed to a predetermined target aggregate size.

The target size of the aggregate depends mainly on the individual application. When used as a polymer filler, this depends on, for example, the proposed treatment technique and the predetermined degree of charge, and process parameters such as the properties and viscosity of the particular plastic should be considered. It can also be adjusted for each application condition and can be used in processes involving, for example, fillers for thermoplastics, fillers for thermosetting resins, injection molding, extrusion or casting resins and film extrusion.

The size of the target aggregate can be achieved through steps such as sieving, sieving-grinding and sorting in the usual steps. Any particulate matter contained in the interior can be removed first. Aggregates having a size of from a few millimeters to a few centimeters are processed in a subsequent process to a predetermined aggregate size. For this purpose, it is possible to use, for example, commercial sieves with different mesh meshes and shedding aids used in vibrating webs. It has been found that the multi-staging / sieving-milling process is advantageous.

To achieve this target aggregate size, after consolidation, and after heat treatment and removal of optional particulates, the agglomerates are preferably first passed through a net having a mesh size of 3 to 4 mm. Using a simple shedding aid, i. E., A rubber ball or a plastic ring, the agglomerates can be broken sufficiently through swinging, usually they have a size of about 30 to 350 microns. When the mesh of the net is 1 mm or less, agglomerates having a diameter of less than 700 mu m, less than 500 mu m, or less than 350 mu m, for example, can be obtained by using a steel ball, preferably a rubber-coated steel ball, during the subsequent sieving.

In the subdivision step, finer aggregates can be prepared in a wide range. For example, aggregate fractions of less than 200 [mu] m, less than 150 [mu] m and less than 100 [mu] m can be separated in decreasing amounts. In order to obtain finer aggregate sizes of less than 350 μm with narrow aggregate size distribution, these microaggregates from the aggregates of less than 350 μm obtained as described above can be sequentially prepared through sieving or fractionation processes. In this manner, agglomerate fractions of, for example, 100 to 200 mu m, 80 to 150 mu m and 150 to 200 mu m can be obtained. Aggregates smaller than 100 mu m are preferably prepared by a fractionation process in order to better observe the upper and lower limit values of the aggregate size.

Separately, the sieved agglomerates can be pulverized with a classifier mill, a tissue roll crusher and a cutting wheel according to a sieving-pulverizing process. For example, dry polishing performed in a ball mill is also possible.

When the structured agglomerates are used for a specific purpose, it is advantageous for the agglomerate size obtained as described above to be subjected to a subsequent special treatment process. Such a treatment process may be exemplified by a wet-chemical method for removing B ₂ O ₃ adhering to the surface, a surface modification using an additive, a coating using a fluidized bed method, and a thermal / oxidative activation treatment. Surface modification with additives can be done, for example, by suspension adsorption. Examples of coatings usable herein include polymers, organometallic compounds, silanes, oils, carboxylic acids, copolymers, hydrolyzed or partially hydrolyzed and partially condensed monomers, and SiO ₂ nanoparticles and surface functionalized nanoparticles such as surface functionalized SiO ₂ nanoparticles and the like. The additives used for surface modification can serve as wetting agents or adhesion promoters.

In another embodiment of the present invention, large blade-shaped agglomerates of about 100 or 200 microns in size, using blade blades with a blade spacing less than the thickness of the agglomerate, such as less than 50 microns, Are crushed, it is possible to produce needles and flake aggregates. This again, as described above, is pulverized and separated through a multistage sieving process to form aggregates. The organized agglomerates prepared in this manner exhibit a reversed preferred orientation of the boron nitride primary particles, with the basal plane perpendicular to the major surface of the flaky aggregate. The tissue index of the organized aggregate produced in this manner is measured to a value of 0.7 or less, preferably 0.5 or less, more preferably 0.35 or less, particularly preferably 0.3 or less. According to the orientation as described above, it is possible to achieve a plane passing thermal conductivity higher than the in-plane thermal conductivity in the filling polymer. This is because the flaky aggregates prepared by this method can be aligned in the filler polymer, especially when the aspect ratio of the aggregates exceeds 2.0. For example, orientation may occur during sheet metal casting or injection molding.

After consolidation or after selective heat treatment, the textured aggregates according to the invention can undergo mechanical processing. Mechanical processing can be carried out, for example, in roller horses in ball-free plastic containers (30% by volume charging time 1 to 2 hours) or in a tumble mixer. As a result of this treatment, the edges and edges of the organized agglomerates can be rounded off and the solids content and thermal conductivity in the polymer-boron nitride composite can be increased.

Unlike the method described for consolidation between two rolls, other methods can also be used to prepare the structured agglomerates according to the invention.

One alternative method is to apply the powder layer by spraying, for example, a boron nitride suspension onto the carrier film. By controlling the evaporation of the suspending medium, the tissue is formed prior to consolidation. Subsequently, the carrier film and the powder layer are consolidated together to further improve the structure. The carrier film may be removed or may be decomposed in a subsequent heat treatment step. The resulting compacted powder layer can be pulverized and sieved as described above to form a structured aggregate.

Another possible method is doctor-blade film casting. The film thus obtained may be compressed or rolled according to the organic binder used, consolidated with a hot roll, and then cut and pulverized into an organized aggregate. Optionally, the aggregates may be heat treated before or after cutting.

The aggregate according to the present invention can be used as a polymer filler, and can be processed into a polymer-boron nitride composite. In the preparation of the filled polymer, the aggregate according to the present invention may be mixed with other known polymer fillers such as aluminum oxide. In the preparation of the filled polymer, it is also possible to use mixtures of different constituents of the aggregates according to the invention, and mixtures of the above-mentioned constituents and primary particles.

Aggregates, i.e., pure boron nitride aggregates and mixed granules (" hybrid flakes ") according to the present invention are all suitable as starting materials for the preparation of boron nitride sintered bodies and boron nitride mixed ceramics. Preferably, the boron nitride sintered body and the boron nitride mixed ceramic are manufactured by hot pressing or hot isostatic pressing. Aggregates used for this purpose are preferably agglomerates which have not undergone the calcination and agglomerates which have been heat-treated at low temperatures up to about 1600 ° C, for example agglomerates which have been treated or calcined to remove the binder. Depending on the high density and high buffer density of the agglomerate according to the present invention, higher mold filling degree and green density can be ensured. Thus, more efficient consolidation is possible than that achieved with conventional cold isostatic compression granulation, pelletization or spray granulation. When the aggregate according to the present invention is used as a starting material for hot pressing, the hot-pressed boron nitride sintered body can be obtained in a form having a very remarkable texture and a very remarkable anisotropic phase. Moreover, the organized agglomerates can be mixed with the non-agglomerated boron nitride powders to serve as nuclei for the crystallization of the hexagonal boron nitride during the reinforcing element or hot pressing. It is particularly advantageous to mix turbulent borosilicate with turbostructured agglomerates. By using the structured agglomerates, the properties of the sintered boron nitride can be improved, for example, the mechanical strength is increased. Also, for example, boron nitride and silicon nitride, boron nitride and zirconium dioxide, and boron nitride mixed ceramic based on boron nitride, zirconium dioxide and silicon carbide can also be produced using the organized agglomerates according to the present invention. Hot pressing is performed in a graphite mold at a temperature of about 1600 to 2000 占 폚 and a pressure of about 25 MPa. In the hot-pressed boron nitride sintered body manufactured using the aggregate according to the present invention, the texture index measured for the sintered body may have a value of at most 120 or more. Tissue index is measured for samples made perpendicular to the hot-pressing direction. Preferably, the tissue index measured in the sintered body has a value of at least 2, more preferably at least 3, more preferably at least 5, more preferably at least 10, particularly preferably at least 20.

The agglomerates according to the present invention can also be used in other applications, for example, raw materials for the synthesis of cubic boron nitride, uncomplicated fillers for heating cartridges, and the like.

Example

The following examples are provided for a detailed description of the present invention.

Example 1

A hexagonal boron nitride powder having a primary particle size (d ₅₀ ) of 3 μm (measured by Mastersizer 2000, Malvern, wet measurement; ESK Ceramics GmbH & Co. KG, BORONID S1) Silicon nitride rolls. The roll width is 150 mm and the roll diameter is 13 cm. The roll is rotated at a speed of 15 rev / min and a force of 1.7 tons is applied. According to this method, the boron nitride powder was roll-consolidated at a throughput of 4 kg / h.

The resultant material is a particulate of flake granules and non-compacted starting material having a thickness of about 50 microns. The obtained material is subjected to heat treatment at 1,200 DEG C for 2 hours under a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size of less than 350 μm, then further sieved to subdivide them into sizes of greater than 210 μm and greater than 100 μm to obtain 55% by weight or less of the above- (Relative to the total amount of heat-treated agglomerates).

Example 2

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resultant material is a particulate of flake granules and non-compacted starting material having a thickness of about 50 microns. This is sieved to less than 100 [mu] m with 46% by weight of the material obtained in roll consolidation and dedusted to separate into the form of fine particles. The separated coarsse fraction is again heat treated at 1200 ° C for 2 hours under a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size of less than 350 μm, further sieved and subdivided into a size of more than 210 μm and a size of more than 100 μm, .

Example 3

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resultant material is a particulate of flake granules and non-compacted starting material having a thickness of about 50 microns. This is sieved to less than 100 [mu] m with 46% by weight of the material obtained in roll consolidation, and is then decomposed to form a particulate form. The separated granules were further heat-treated at 1600 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 m, then further sieved and subdivided into sizes larger than 210 m and larger than 100 m to obtain a 4 wt% .

Example 4

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resultant material is a particulate of flake granules and non-compacted starting material having a thickness of about 50 microns. This is sieved to less than 100 [mu] m with 46% by weight of the material obtained in roll consolidation, and is then decomposed to form a particulate form. The separated granules were further heat-treated at 1950 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 μm, then further sieved and subdivided into sizes larger than 210 μm and larger than 100 μm to obtain a 3 wt% .

Example 5

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resulting material is secondarily consolidated at a throughput of 5.8 kg / h. The resultant is a granulate of flake-shaped granules and a non-compacted starting material granules having a thickness of about 50 to 100 μm. It is sieved to less than 100 [mu] m with 26% by weight of the material obtained in roll consolidation, and is then decomposed into fine particulate form.

The separated granules were further heat-treated at 1950 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 μm, then further sieved and subdivided into sizes larger than 210 μm and larger than 100 μm to obtain a 3 wt% .

Example 6

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resulting material is again subjected to secondary consolidation at a throughput of 5.8 kg / h and tertiary consolidation at a throughput of 7 kg / h. After each pass through the rolls, the granules obtained are sieved to less than 100 microns and damped, and finally separated into a particulate form by dampening with 5 weight percent of the material obtained in roll consolidation. The thickness of the agglomerates obtained with the flakes is about 50 to 200 mu m.

The separated granules were further heat-treated at 1950 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 m, then further sieved and subdivided into sizes larger than 210 m and larger than 100 m to obtain a 4 wt% .

Example 7 (I)

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resulting material is again subjected to secondary consolidation at a throughput of 5 kg / h and tertiary consolidation at 6.5 kg / h. Between the consolidation operations, the fine particles (less than 100 mu m) were measured but not separated. The resulting granulate is in the form of a flaky granulate having a thickness of from 50 to 200 탆 which again separates into a particulate form by sieving to less than 100 탆 with 15% by weight of the material obtained in roll consolidation.

The separated granules were further heat-treated at 1200 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates are sieved to a size smaller than 350 μm, and further sieved and subdivided.

Example 7 (I-A)

From Example 7 (I), an agglomerate having a size of less than 100 m was sieved.

Example 7 (IB)

From Example 7 (I), an aggregate of 100 to 210 탆 was sieved.

Example 7 (IC)

From Example 7 (I), an aggregate of 210 to 350 탆 was sieved.

Table 1 shows the tissue index values determined for these aggregates and the specific surface area values according to the BET method (nitrogen adsorption, Beckmann-Coulter) in Examples 7 (I-A, I-B and I-C). Table 1 also shows the aspect ratios measured from SEM photographs, for example with respect to Example 7 (I-A and I-B).

Example 7 (II)

Example 7 (I) was repeated except that the granules separated after roll consolidation for 3 times were heat-treated at 1600 ° C for 2 hours under a nitrogen atmosphere.

Example 7 (II-A)

From the Example 7 (II), an agglomerate having a size of less than 100 m was sieved.

Example 7 (II-B)

An aggregate of 100 to 210 탆 was sieved from Example 7 (II).

Example 7 (II-C)

An aggregate of 210 to 350 탆 was sieved from Example 7 (II).

Table 1 shows the texture index values determined for these aggregates, the specific surface area values according to the BET method (nitrogen adsorption, Beckmann-Coulter), and the aspect ratios measured from the SEM photographs in Examples 7 (II-B and II- .

Example 7 (III)

Example 7 (I) was repeated except that the granules separated after roll consolidation for 3 times were heat-treated at 1950 ° C for 2 hours under a nitrogen atmosphere.

Example 7 (III-A)

From the Example 7 (III), an agglomerate having a size of less than 100 m was sieved.

The average aggregate size (d ₅₀ ) is 78 μm.

Example 7 (III-B)

An agglomerate of 100 to 210 탆 was sieved from Example 7 (III).

The average aggregate size (d ₅₀ ) is 156 μm.

Example 7 (III-C)

An aggregate of 210 to 350 탆 was sieved from Example 7 (III).

The average aggregate size (d ₅₀ ) is 347 탆.

Table 1 shows the texture index values determined for these aggregates, the specific surface area values according to the BET method (nitrogen adsorption, Beckmann-Coulter), and the aspect ratios measured from the SEM photographs in Examples 7 (III-B and III- .

Example 8

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 μm (measured by Mastersizer 2000, Malvern, wet measurement; ESK Ceramics GmbH & Co. KG, BORONID S1) was sprayed at 5.2 kg / h Roll-consolidation as in Example 1 at throughput.

The granulate having a thickness of about 50 占 퐉 and obtained in the form of flakes contains 28% by weight of powders of less than 100 占 퐉. Without subjecting to a primary separation process for the fine particles, the material is heat treated at 1200 DEG C for about 2 hours under a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a net and a netting aid, and then pulverized to less than 700 μm. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 μm, then further sieved and subdivided into sizes larger than 210 μm and larger than 100 μm to obtain a slurry having a size of less than 100 μm and containing 30% .

Example 9

Hexagonal boron nitride powder having a primary particle size (d ₅₀ ) of 15 μm was roll-consolidated as in Example 1 at a throughput of 5.2 kg / h using a vibrating chute.

The granulate having a thickness of about 50 mu m and obtained in the form of a flake is again sieved to less than 100 mu m together with 28 wt% of the material obtained in roll consolidation to separate into a particulate form.

The separated granules were further heat-treated at 1200 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size of less than 350 μm, further sieved and subdivided into a size of more than 210 μm and a size of more than 100 μm, .

Example 10

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 탆 was continuously supplied using a vibration chute and roll-consolidated as in Example 1 at a throughput of 5.2 kg / h.

The granulate having a thickness of about 50 mu m and obtained in the form of a flake is sieved to less than 100 mu m together with 26 wt% of the material obtained in roll consolidation and is dispersed in a particulate form by volatilization.

The separated granules were further heat-treated at 1600 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 m, then further sieved and subdivided into sizes larger than 210 m and larger than 100 m to obtain a 4 wt% .

Example 11

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 탆 was continuously supplied using a vibration chute and roll-consolidated as in Example 1 at a throughput of 5.2 kg / h.

The granulate having a thickness of about 50 mu m and obtained in the form of a flake is sieved to less than 100 mu m together with 26 wt% of the material obtained in roll consolidation and is dispersed in a particulate form by volatilization.

The separated granules were further heat-treated at 1950 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 μm, then further sieved and subdivided into sizes larger than 210 μm and larger than 100 μm to obtain a 2 wt% .

Example 12

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 탆 was continuously supplied using a vibration chute and roll-consolidated as in Example 1 at a throughput of 5.2 kg / h.

The resulting material is secondarily consolidated at a throughput of 8 kg / h. The granules having a thickness of about 50 to 100 mu m and obtained in the form of flakes are sieved to less than 100 mu m together with 16 wt% of the material obtained in roll consolidation and separated into fine particulate form by vibration dampening.

The separated granules were heat-treated at 1950 ° C for 2 hours under a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 μm, then further sieved and subdivided into sizes larger than 210 μm and larger than 100 μm to obtain a 3 wt% .

Example 13

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 탆 was continuously supplied using a vibration chute and roll-consolidated as in Example 1 at a throughput of 5.2 kg / h.

The resultant material is again subjected to secondary consolidation at a throughput of 8 kg / h and tertiary consolidation at a throughput of 16 kg / h. The granulate having a thickness of about 50 to 200 m and obtained in the form of flakes is sieved to less than 100 [mu] m with 5% by weight of the material obtained in roll consolidation and separated into fine particulate forms.

The separated granules were further heat-treated at 1950 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size smaller than 350 m, then further sieved and subdivided into sizes larger than 210 m and larger than 100 m to obtain a 4 wt% .

Example 14 (I)

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 μm was continuously supplied using a vibration chute and roll-consolidated as in Example 1 at a throughput of 5 kg / h.

The resulting material is then third consolidated at a throughput of 7.9 kg / h and secondary consolidation and throughput of 15.9 kg / h. Between the consolidation operations, the fine particles (less than 100 mu m) were measured but not separated. The resulting granulate is granulated in the form of flakes having a thickness of from 50 to 200 탆, which is again sieved to less than 100 탆 with 12% by weight of the material obtained in roll consolidation and separated into fine particulate form .

The separated granules were further heat-treated at 1200 ° C for 2 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates are sieved to a size smaller than 350 μm, and further sieved and subdivided.

Example 14 (I-A)

From Example 14 (I), an agglomerate having a size of less than 100 m was sieved.

Example 14 (IB)

From Example 14 (I), an aggregate of 100 to 210 탆 is sieved and sieved.

Example 14 (IC)

From Example 14 (I), an aggregate of 210 to 350 탆 was sieved.

The tissue index values determined for these aggregates and the specific surface area values according to the BET method (nitrogen adsorption, Beckmann-Coulter) are shown in Table 1 in Examples 14 (I-A, I-B and I- Table 1 also shows the aspect ratios measured from SEM photographs, for example, in relation to Example 14 (I-C).

Example 14 (II)

Example 14 (I) was repeated except that the granules separated after roll consolidation for 3 times were heat-treated at 1600 ° C for 2 hours under a nitrogen atmosphere.

Example 14 (II-A)

From the Example 14 (II), an agglomerate having a size of less than 100 m was sieved.

Example 14 (II-B)

An aggregate of 100 to 210 탆 is sieved from Example 14 (II).

Example 14 (II-C)

An aggregate of 210 to 350 탆 was sieved from Example 14 (II).

Table 1 shows the tissue index values determined for these aggregates and the specific surface area values according to the BET method (nitrogen adsorption, Beckmann-Coulter) in Example 14 (II-A, II-B and II-C). Table 1 also shows the aspect ratios measured from SEM photographs, for example, in relation to Example 14 (II-C).

Example 14 (III)

Example 14 (I) was repeated except that the granules separated after roll consolidation for 3 times were heat-treated at 1950 ° C for 2 hours under a nitrogen atmosphere.

Example 14 (III-A)

From the Example 14 (III), an aggregate of less than 100 탆 was sieved.

Example 14 (III-B)

An aggregate of 100 to 210 탆 was sieved from Example 14 (III).

Example 14 (III-C)

An aggregate of 210 to 350 탆 is sieved from Example 14 (III).

Table 1 shows the texture index values determined for these aggregates, the specific surface area values according to the BET method (nitrogen adsorption, Beckmann-Coulter), and the aspect ratios measured from the SEM photographs in Example 14 (III-C).

Example 15

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was roll-consolidated as in Example 1 at a throughput of 4 kg / h using a vibration chute.

The resulting material is a particulate of flake granules and non-compacted starting material having a thickness of about 50 μm. This is sieved to less than 100 [mu] m with 46% by weight of the material obtained from the roll consolidation, and is separated into fine particulate form.

The separated granules were further heat-treated at 1900 ° C for 12 hours in a nitrogen atmosphere. The heat-treated flaky aggregate is first pulverized to a size of less than 3 mm using a netting and a netting aid, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates were sieved to a size of less than 350 μm, further sieved and subdivided into a size of more than 210 μm and a size of more than 100 μm, .

The specific surface area was measured by the BET method (nitrogen adsorption, Beckmann-Coulter) for the agglomerates of 210 to 350 mu m. The organized aggregate has a very low density of 0.99 m2 / g and the tissue index, measured for this aggregate, is 3.1.

Example 16

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h.

The resulting material is again subjected to secondary consolidation at a throughput of 5 kg / h and tertiary consolidation at a throughput of 6.5 kg / h. The resultant is a flake-like granulate having a thickness of about 50 to 200 탆, which is again sieved to less than 100 탆 with 15% by weight of the material obtained in roll consolidation and separated into fine particulate forms.

The separated granules are first pulverized to a size of less than 3 mm by using a net and a net auxiliary, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates are sieved to a size smaller than 350 μm, further sieved and subdivided into sizes of 210 to 350 μm. Table 1 shows the tissue indexes measured for these aggregates.

Example 17

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 μm was continuously supplied using a vibration chute and roll-consolidated as in Example 1 at a throughput of 5 kg / h.

The resulting material is then third consolidated at a throughput of 7.9 kg / h and secondary consolidation and throughput of 15.9 kg / h. The resultant is a flake-like granulate having a thickness of about 50 to 200 탆, which is again sieved to less than 100 탆 with 15% by weight of the material obtained in roll consolidation and separated into fine particulate forms.

The separated granules are first pulverized to a size of less than 3 mm by using a net and a net auxiliary, and then pulverized to less than 700 탆. Finally, the resultant flaky agglomerates are sieved to a size smaller than 350 μm, further sieved and subdivided into sizes of 210 to 350 μm. Table 1 shows the tissue indexes measured for these aggregates.

Example 18

BN-Al ₂ O ₃ spray granules having an average granule size (d ₅₀ ) of 100 μm and an Al content of 6 wt% were continuously fed using a vibrating chute and fed at a throughput of 7 kg / h as in Example 1 - Consolidate.

The resulting material is again subjected to secondary consolidation at a throughput of 12.9 kg / h and tertiary consolidation at a throughput of 19.9 kg / h. The granulate having a thickness of about 50 to 200 m and obtained in the form of flakes is sieved to less than 100 [mu] m with 22% by weight of the material obtained in roll consolidation and separated into fine particulate forms. These flakes have a diameter of a few centimeters. They can be used as a polymer filler when heat-treated in air at 1000 ° C for 1 hour.

Example 19

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and rolled-up as in Example 1 at a throughput of 4 kg / h in the first pass. After the second pass (throughput of 5 kg / h) and the third pass (throughput of 6.5 kg / h), the agglomerates were produced in the shape of flakes with a thickness of about 50 to 200 μm and a diameter of several centimeters.

A small disc (3.5 cm 2) was cut from the obtained plate (flake), and its tissue index was measured as 11.4.

The densities identified in the geometric and buoyancy measurements are shown in Table 2.

Example 20

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 3 탆 was continuously supplied by using a vibration chute and rolled-up as in Example 1 at a throughput of 4 kg / h in the first pass. After the second pass (throughput of 5 kg / h) and the third pass (throughput of 6.5 kg / h), the aggregates were produced in the shape of flakes with a thickness of about 50 to 200 μm and a diameter of several centimeters.

The agglomerates were heat treated under nitrogen at 1950 ° C for 2 hours.

A small disc (3.5 cm 2) was cut from the obtained plate (flake), and its tissue index was measured at 7.5.

The densities identified in the geometric and buoyancy measurements are shown in Table 2.

Example 21

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 탆 was continuously supplied using a vibration chute, and rolled-up as in Example 1 at a throughput of 5 kg / h in the first pass. After the secondary passage (throughput of 7.9 kg / h) and the tertiary passage (15.9 kg / h), the agglomerates were produced in the shape of flakes with a thickness of about 50 to 200 μm and a diameter of several centimeters.

A small disc (3.5 cm 2) was cut from the obtained plate (flake), and its tissue index was measured at 14.4.

The densities identified in the geometric and buoyancy measurements are shown in Table 2.

Example 22:

Hexavalent boron nitride powder having a primary particle size (d ₅₀ ) of 15 탆 was continuously supplied using a vibration chute, and rolled-up as in Example 1 at a throughput of 5 kg / h in the first pass. After the secondary passage (throughput of 7.9 kg / h) and the tertiary passage (15.9 kg / h), the agglomerates were produced in the shape of flakes with a thickness of about 50 to 200 μm and a diameter of several centimeters.

The agglomerates were heat treated under nitrogen at 1950 ° C for 2 hours.

A small disc (3.5 cm 2) was cut from the obtained plate (flake), and its tissue index was measured as 66.9.

The densities identified in the geometric and buoyancy measurements are shown in Table 2.

Example 23

Example 22 was repeated except that the agglomerates were heat treated at 2050 ° C for 2 hours under nitrogen, not at 1950 ° C.

A small disc (3.5 cm 2) was cut from the obtained plate (flake), and its tissue index was measured as 108.

The densities identified in the geometric and buoyancy measurements are shown in Table 2.

In the following Examples 24 to 32 and Comparative Examples, the boron nitride aggregates were processed and prepared from filled epoxides (epoxide-boron nitride composite). These charged epoxide samples can be used to obtain comparative values for the thermal conductivity of different boron nitride aggregates. Larger thermal conductivity values can be achieved in the use of other polymers, for example, in the injection molding of thermoplastics.

Example 24 (I-A)

Organized agglomerates used as fillers in epoxides, filling degree 43%, random alignment

53 g of flake-shaped structured agglomerates from Example 7 (I) are dispersed in a mixture of 70 g of epoxide and hardener (EpoFix, Struers, Willich, Germany) using a blade stirrer. At a pressure of 0.2 bar, air is blown off with a vacuum stirrer. The mixture is poured into a dish and solidified.

To measure the thermal conductivity, a plate of 10 x 10 x 2 mm is prepared from the mold. The thermal conductivity (TC) is determined by measuring the thermal diffusivity (a), the specific heat capacity (c _P ) and the density (D) and is calculated from these values according to the following formula: TC = a * c _P * D. "a" and "c _p " are measured using NanoflaSh LFA 447 (Netzsch, Selb, Germany) at room temperature for a sample having a size of 10 x 10 x 2.. Density is determined by weighing a precisely formed sample and measuring its geometric dimensions.

The measured values obtained in relation to the thermal conductivity are shown in Table 3.

(II-A, II-B and III-C), Example 24 ( III-A, III-B and III-C) and Example 25

Organized agglomerates used as fillers in epoxides, filling degree 43%, random alignment

Example 24 (I-A) was repeated except that the flaky organized agglomerates according to each Example ("filler" item) listed in Table 3 were used in an amount of 53 g.

Example 26

Organized agglomerates used as fillers in epoxides, filling degree 43%, alignment by preferential alignment , plane passing

53 g of flake-shaped structured agglomerates from Example 7 (III-C) are dispersed in a mixture of 70 g of epoxide and curing agent (EpoFix, Struers, Willich, Germany) using a blade stirrer. At a pressure of 0.2 bar, air is blown off with a vacuum stirrer. The mixture is cast between two acrylic glass discs spaced 2 mm apart, and this mixture solidifies between these acrylic glass discs. 10 x 10 x 2 ㎣ from solidification plate Size, and the thickness of this coagulation plate is equal to the height of the sample.

The thermal conductivity is measured as described in Example 24 (I-4) (Table 3). Due to the alignment of the textured agglomerates with preferential orientation, the measured thermal conductivity is a value of " plane passing " over the basal plane of the boron nitride primary particle thin film layer.

Example 27

Organized agglomerates used as fillers in epoxides, filling degree 43%, alignment by preferential alignment , planar

From the solidification plate of Example 26, 10 x 10 x 2 ㎣ 5 &lt; / RTI &gt; These thin film layers are bonded to each other to form a cube having an edge length of 10 mm. Next, the cube is rotated so that the five cross sections of the thin film layer in the laminate are upward. The upper and lower surfaces of the stacked layers arranged in this manner are polished to a thickness of 2 mm. Separately, 10 x 10 x 2 x Sized thin film layer is formed by joining five divided pieces to each other.

The thermal conductivity is measured as described in Example 24 (I-A) (Table 3). Due to the alignment of the textured agglomerates with preferential orientation, the measured thermal conductivity is a value "in-plane" with respect to the basal plane of the boron nitride primary particle thin film layer.

The measured in-plane value is larger than the plane passing value in Example 26. [

Example 28

Organized agglomerates used as fillers in epoxides, filling degree 43%, alignment by preferential alignment , plane passing

3% boronide SCP1 (boron nitride powder having an average particle size of 1 mu m, ESK Ceramics GmbH & Co. KG), 24% boronoid S15 (boron nitride having an average particle size of 15 mu m, ESK Ceramics) Of the flakes of Example 7 (III-C). 53 g of the mixture was treated according to Example 26 and cast between two acrylic glass plates to produce a solidified plate. A sample of thermal conductivity was prepared from the above solidification plate as in Example 26 and the thermal conductivity was measured (Table 3).

Example 29

Organized agglomerates used as fillers in epoxides, filling degree 43%, alignment by preferential alignment , planar

Repeat the procedure of Example 28 except that five thin film layers having a size of 10 x 10 x 2 mm are prepared from the solidification plate. These are processed as in Example 27 to produce in-plane thermal conductivity samples and the thermal conductivity in the plane is measured (Table 3).

The in-plane value is larger than the plane passing value in Embodiment 28. [

Example 30

53 g of flakes obtained from Example 7 (III-C) were mechanically treated for 2 hours in a tumble mixer. This flake was processed as in Example 24 (I-A), and a sample of thermal conductivity was prepared and the thermal conductivity was measured (Table 3).

Example 31

Organized agglomerates (no heat treatment) used as filler in epoxide, filling degree 59%

105 g of 210-350 urn aggregates obtained from Example 17 are dispersed in a mixture of 70 g of epoxide and curing agent (EpoFix, Struers, Willich, Germany) using a blade stirrer. At a pressure of 0.2 bar, air is blown off with a vacuum stirrer. The mixture is poured into a dish and solidified.

In order to measure the thermal conductivity, a thin film layer of 10 x 10 x 2 mm is prepared from the mold. The thermal conductivity is measured as in Example 24 (I-A) and the measured thermal conductivity values are shown in Table 3. [

Example 32

Organized agglomerate (heat treated) used as filler in epoxide, filling degree 59%

Example 31 was repeated except that the aggregate of 105 g obtained in Example 14 (III-C) was treated in place of the aggregate obtained in Example 32. [

The measured thermal conductivity values are greater than in Example 31 (Table 3).

Example 33:

Hot pressing using organized agglomerates

The hexagonal boron nitride powder having a primary particle size (d ₅₀ ) of 15 μm (measured by Mastersizer 2000, Malvern, wet measurement; ESK Ceramics GmbH & Co. KG, BORONID S1) was continuously supplied kg / h. &lt; / RTI &gt; The resulting material is then third consolidated at a throughput of 7.9 kg / h and secondary consolidation and throughput of 15.9 kg / h. The granules having a thickness of 200 mu m and obtained in the form of a flake are sieved to less than 100 mu m together with 12 wt% of the material obtained in roll consolidation, and are dispersed in a particulate form. The size of the obtained flakes is 1 to 3 cm.

The flaky agglomerates prepared in this manner were placed in a hot-pressing mold (diameter 7.2 cm, height 12 cm). Typically less than 250 grams of BN powder, more than 500 grams of material can be filled into the same volume of hot-press molds. Next, hot-pressing was carried out at a temperature of 1800 캜 and a holding time of 1 hour at a pressure of 23 MPa. The hot-pressed boron nitride sintered body thus obtained had a density of 2.09 g / cm &lt; 3 &gt; and very excellent texture. The tissue indexes measured in the hot-pressed sintered body have a size of 2 mm x 1 cm x 1 cm and are 118.3 for a sample made perpendicular to the hot-squeeze direction. By comparison, the tissue index measured at a known hot-pressed boron nitride sinter (for example, MYCROSINT S, ESK Ceramics GmbH &amp; Co. KG) is only about 1.8 at most.

Example 34:

Hot-pressing with structured agglomerates and turbo-static boron nitride

A structured agglomerate was prepared as in Example 33. However, hexagonal boron nitride powder having an initial particle size (d ₅₀ ) of 3 탆 was used for rolling consolidation. Next, a structured agglomerate having a size of 1 to 3 cm was mixed with turbo-static nitric boron in a ratio of 1: 1 and placed in a hot-press mold (diameter 7.2 cm, height 12 cm) Hot-pressing was performed at a pressure of 23 MPa with a holding time of 90 minutes. The obtained hot-pressed boron nitride sintered body had a density of 2.14 g / cm 3. The four-point bending strength measured by this sintered body is 153 MPa and the Brinell hardness is 49.8. In comparison, hot-pressed sintered bodies of equivalent size were prepared from boron nitride powders having an initial particle size (d ₅₀ ) of 3 μm at the same hot-compression conditions. The bending fracture strength measured in this comparative sintered body is 75 MPa at a density of 2.03 g / cm 3 and a Brinell hardness of 31.8.

Example 35

Hot pressing using organized agglomerates

Hexagonal boron nitride powder having a primary particle size (d ₅₀ ) of 3 μm (measured by Mastersizer 2000, Malvern, wet measurement; ESK Ceramics GmbH & Co. KG, BORONID S1) and a B ₂ O ₃ content of 3 wt% And continuously fed with a vibration chute and roll-consolidated as in Example 1 at a throughput of 4 kg / h. The resulting material is again subjected to secondary consolidation at a throughput of 5.8 kg / h and tertiary consolidation at a throughput of 7 kg / h. The granules having a thickness of 200 mu m and obtained in the form of a flake are sieved to less than 100 mu m together with 4 wt% of the material obtained in roll consolidation and are dispersed in the form of fine particles by vibration dampening. The size of the obtained flakes is 1 to 3 cm.

The flaky agglomerates prepared in this manner were placed in a hot-pressing mold (diameter 7.2 cm, height 12 cm). Next, hot-pressing was carried out at a temperature of 1800 캜 and a holding time of 1 hour at a pressure of 23 MPa. The obtained hot-pressed boron nitride sintered body had a density of 2.11 g / cm 3. The tissue indexes measured in the hot-pressed sintered body have a size of 2 mm x 1 cm x 1 cm and are 8.9 for a sample made perpendicular to the hot-squeeze direction.

Comparative Example 1

Unorganized aggregate

Hot-crushed boron nitride (MYCROSINT S, ESK Ceramics GmbH & Co. KG) is pre-fractured using a jaw crusher and ground again into a hammer mill (mesh insert of 4 mm holes). A sieving treatment is carried out to obtain aggregates in a predetermined range, that is, 100 to 210 탆 and 210 to 350 탆

Table 1 shows the values measured at agglomerates of 100 to 210 탆 in relation to the specific surface area (nitrogen adsorption, Beckmann-Coulter) according to the tissue index and the BET method.

Comparative Example 1 (I)

Unstructured aggregates used as fillers in epoxides, filling degree 43%, random alignment

53 g of agglomerate (agglomerate of 100 to 210 탆, average agglomerate size (d ₅₀ ) of 170 탆) obtained from Comparative Example 1 was treated according to Example 24 (IA) to prepare a thermal conductivity sample, (Table 3).

Comparative Example 1 (II)

Unstructured agglomerates used as fillers in epoxides, filling degree 43%, making "plane pass" samples

53 g of agglomerate (agglomerate of 100 to 210 탆, average agglomerate size (d ₅₀ ) of 170 탆) obtained from Comparative Example 1 was treated according to Example 19 to form a solidification plate, a thermal conductivity sample was prepared, The thermal conductivity is measured (Table 3).

Comparative Example 1 (III)

Unstructured agglomerates used as fillers in epoxides, filling 43%, "in-plane" sample production

53 g of agglomerate (agglomerate of 100 to 210 탆, average agglomerate size (d ₅₀ ) of 170 탆) obtained from Comparative Example 1 is treated according to Example 19.

Five thin film layers having a size of 10 x 10 x 2 mm were prepared from the solidification plate obtained from Comparative Example 1 (II). This is treated as in Example 20 to produce a planar thermal conductivity sample and the thermal conductivity is measured in the plane (Table 3).

Plane value is only slightly larger than the plane passing value in Comparative Example 1 (II).

Comparative Example 2

Unorganized aggregate

Boron nitride agglomerates are prepared according to Example 3 of WO 2005/021428 A1.

For this purpose, hexagonal boron nitride powder having a primary particle size (d ₅₀ ) of 1 μm (measured by Mastersizer, ESK Ceramics GmbH & Co. KG, BORONID S1) is compacted by cold-isostatic pressing at a pressure of 1350 bar. The resulting compact is preliminarily crushed and pulverized by sieving and a homogenization-pulverization treatment to obtain a fine particle fraction of 100 to 210 탆. The granules are heat treated under nitrogen at 1900 ° C for 12 hours.

The resulting sintered cake of the granules is pulverized again by sieving and sieving-finishing to make a particle fraction of 100 to 210 탆. The average aggregate size (d ₅₀ ) measured by laser diffraction is 150 μm (dry measurement, Mastersizer 2000, Malvern).

Table 1 shows the values measured at agglomerates of 100 to 210 탆 in relation to the specific surface area (nitrogen adsorption, Beckmann-Coulter) according to the tissue index and the BET method.

Comparative Example 2 (I)

Unstructured aggregates used as fillers in epoxides, filling degree 43%, random alignment

The aggregate of 53 g obtained in Comparative Example 2 was treated according to Example 17 (I-A) to prepare a sample of thermal conductivity and the thermal conductivity was measured (Table 3).

Comparative Example 2 (II)

Unstructured agglomerates used as fillers in epoxides, filling degree 43%, making "plane pass" samples

53 g of the agglomerate obtained from Comparative Example 2 was treated according to Example 26 to form a solidification plate, and a thermal conductivity sample was prepared and the plane thermal conductivity was measured (Table 3).

Comparative Example 2 (III)

Unstructured agglomerates used as fillers in epoxides, filling 43%, "in-plane" sample production

From the solidification plate obtained from Comparative Example 2 (II), five thin film layers each having a size of 10 x 10 x 2 mm were prepared. This is treated in the same manner as in Example 27 to prepare an in-plane thermal conductivity sample and the thermal conductivity is measured in the plane (Table 3).

Plane value is only slightly larger than the plane passing value in Comparative Example 2 (II).

Comparative Example 3

10% Boronide SCP1 (boron nitride powder having an average particle size of 1 占 퐉, ESK Ceramics GmbH & Co. KG) and 90% boronoid S15 (boron nitride powder having an average particle size of 15 占 퐉, ESK Ceramics GmbH & ) Were processed as described in Example 24 (IA) above, and a thermal conductivity sample was prepared and the thermal conductivity was measured (Table 3).

Example Organization index BET [m &lt; 2 &gt; / g] Aspect ratio 7 (I-A) 1.6 16.65 1.8 7 (I-B) 2.3 18.43 3.3 7 (I-C) 2.9 18.63 n.d. 7 (II-B) 2.5 8.77 3.3 7 (II-C) 3.1 8.71 6.8 7 (III-B) 3.4 7.54 3.5 7 (III-C) 4.0 7.61 4.8 14 (I-A) 7.5 6.35 n.d. 14 (I-B) 16.4 7.19 n.d. 14 (I-C) 17.6 8.49 4.4 14 (II-A) 8.7 2.27 n.d. 14 (II-B) 22.1 2.26 n.d. 14 (II-C) 41.5 2.39 7.1 14 (III-C) 40.5 1.69 7.6 15 3.1 0.99 n.d. 16 6.1 n.d. n.d. 17 7.7 n.d. n.d. Comparative Example 1 1.4 2.79 n.d. Comparative Example 2 1.5 6.76 n.d.

n.d .: Not measured

Example Buoyancy density
[g / cm3] Geometric measurement density
[g / cm3] 19 2.24 2.11 20 2.18 2.04 21 2.15 2.00 22 2.05 1.92 23 2.14 2.05

Example Filler Thermal conductivity
[W / m * K] 24 (I-A) 7 I) A) 1.06 24 (I-B) 7 I) B) 1.35 24 (I-C) 7 I) C) 1.03 24 (II-A) 7 II) A) 1.35 24 (II-B) 7 II) B) 1.20 24 (II-C) 7 II) C) 1.67 24 (III-A) 7 III) A) 3.15 24 (III-B) 7 III) B) 2.13 24 (III-C) 7 III) C) 2.26 25 14 III) C) 1.90 26 7 III) C) 1.74 27 7 III) C) 2.59 28 3% SCP1, 24% boronide S15, 73% Example 7 III) Aggregate from C) 2.33 29 3% SCP1, 24% boronide S15, 73% Example 7 III) Aggregate from C) 3.19 30 7 III) C) Round processing 2.32 31 17 1.80 32 14 III) C) 2.40 Comparative Example 1 (I) Comparative Example 1 1.26 Comparative Example 1 (II) Comparative Example 1 1.15 Comparative Example 1 (III) Comparative Example 1 1.24 Comparative Example 2 (I) Comparative Example 2 2.26 Comparative Example 2 (II) Comparative Example 2 2.02 Comparative Example 2 (III) Comparative Example 2 2.17 Comparative Example 3 10% SCP1, 90% boronoid S15 1.15

Claims (11)

A boron nitride aggregate consisting of only layered hexagonal boron nitride primary particles and having a preferred orientation and aggregating with each other,
The boron nitride primary particles are firstly oriented and aggregated with each other in such a manner that the thin film layer planes of the boron nitride primary particles are arranged in parallel with each other,
Wherein the ratio of the formed surface to the entire surface of the flaky aggregate is 10% or more, and the ratio of the formed surface to the whole surface is determined by the following equation:
Formation surface ratio [%] = 2 x frontal area / total area x 100
In this formula,
The frontal area is the aggregate diameter x the aggregate diameter, the total area is 2 x total area + 4 x the lateral area, and the lateral area is the aggregate thickness x aggregate diameter. The aggregate of boron nitride according to claim 1, wherein the tissue index measured in the flaky aggregate is not less than 1.5 and the tissue index is measured in an X-ray diffraction diagram and is determined by the following equation:

In this equation, TI is the tissue index, I _{(002), the sample} is The intensity of the (002) reflection measured in the X-ray diffraction diagram, I ₍₁₀₀₎ The intensity of the (100) reflection measured in the X-ray diffraction diagram. The aggregate of boron nitride according to claim 1, wherein the tissue index measured in the flaky aggregate is less than or equal to 0.7 and the tissue index is determined in an X-ray diffraction diagram and is determined by the following equation:

In this equation, TI is the tissue index, I _{(002), the sample} is The intensity of the (002) reflection measured in the X-ray diffraction diagram, I ₍₁₀₀₎ The intensity of the (100) reflection measured in the X-ray diffraction diagram. The aggregate of boron nitride according to claim 1, wherein the flake aggregate has a density of 1.6 g / cm 3 or more. The aggregate of boron nitride according to claim 1, wherein the flaky aggregate has a thickness of 10 to 500 mu m. The aggregate of claim 1, wherein the average aggregate size (d ₅₀ ) is at most 500 μm. The aggregate of boron nitride according to claim 1, wherein the boron nitride primary particle further comprises a polymer or particles selected from the group consisting of carbide, boride, nitride, oxide, hydroxide, carbon and metal. The method according to claim 1, wherein the aggregate is surface-modified with an additive, and the additive is selected from the group consisting of a polymer, an organometallic compound, a silane, an oil, a carboxylic acid, a monomer, and a nanoparticle. . A polymer-boron nitride composite comprising the flaky boron nitride aggregate according to claim 1. A boron nitride sintered body obtained by sintering the flake-shaped boron nitride aggregate according to claim 1, comprising hexagonal boron nitride. 11. The boron nitride sintered body according to claim 10, wherein the hexagonal boron nitride contained in the sintered body has a structure index of 2 or more, the structure index is measured in an X-ray diffraction diagram, and is determined by the following formula:

In this equation, TI is the tissue index, I _{(002), the sample} is The intensity of the (002) reflection measured in the X-ray diffraction diagram, I ₍₁₀₀₎ The intensity of the (100) reflection measured in the X-ray diffraction diagram.

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